1. Field of the Invention
The present invention relates generally to an improved automatic seat positioning device for a driver's seat of a vehicle, and more specifically to a device for selecting a desired driving position of a driver's seat by rotating a reversible motor and engaging the motor with an electromagnetic clutch associated with each seat member, wherein a seat positional data obtained by counting the number of rotations of the motor is corrected to prepare for a correct return from the present seat position to an originally set seat position.
2. Description of the Prior Art
A motor-powered seat has been developed which can adjust a driver's seat to a desired position by means of a reversible motor with the driver sitting on the seat, wherein the adjusted seat position is once stored to return the adjusted seat position to an originally adjusted seat position automatically.
Such a conventional seat positioning device comprises: (a) a seat actuating mechanism comprising (1) a reversible motor, (2) a plurality of actuators each located within the seat member for actuating the associated seat member to move at a desired position in a normal or reverse direction within an adjustable range specified depending on the seat member, (3) a plurality of electromagnetic clutches each operatively engaged with the motor for transmitting a rotating force of the motor to the corresponding actuator at an output shaft of the motor so as to move the corresponding seat member toward the desired position, and (4) a motor drive circuit, having a plurality of manual reversible switches each provided for specifying an adjustable direction of the individual seat members, which energizes the motor to rotate in a normal or reverse direction with the motor engaged with one of the electromagnetic clutches depending on which of the manual switches is operated and which moving direction of the seat member through the associated manual reversible switch is specified; (b) a seat position control circuit connected to the reversible motor and motor drive circuit of said seat actuating mechanism which detects the positions of the individual seat members from the moved distances along the adjustable directions determined depending on the individual seat members by counting the number of rotations of the reversible motor, stores the counted seat positional data, and actuates the motor drive circuit to rotate the motor in the normal or reverse direction on a basis of the stored seat positional data when the seat position is changed to return to an originally set position.
It should be noted that the conventional seat positioning device is applied to such a driver's seat comprising the seat members, i.e., a seat freely supported on the vehicle body which can adjust a front-and-rear position thereof and an upward-and-downward position thereof with respect to the vehicle body, a seat back which can adjust a tilted angle thereof with respect to the vehicle body and can adjust a lumbar support position thereof, a seat cushion which can adjust an inclined angle thereof with respect to the seat, and a head restraint which can adjust an upward-and-downward position thereof.
The control circuit described above comprises: (a) a rotation number detector attached about the output rotating shaft of the reversible motor which generates and output pulses according to the number of rotations of the motor; (b) a plurality of reversible counters each provided for one of the adjustable directions of the seat members and connected to the rotation number detector for counting the number of pulses received from the rotation number detector incrementally or decrementally depending on the rotational direction of the motor; (c) a memory connected to the seat position data reversible counters for storing the counted values of the seat position data reversible counters into specified addresses thereof when a memory switch and one of the address switches provided for different drivers on an associated operation panel are operated; (d) a comparator connected to the memory and to the reversible counters via a data selector which operatively compares the stored seat positional data with the presently counted values of the individual reversible counters; and (e) a centralized control unit connected to the comparator which actuates the motor drive circuit to rotate the motor in the normal or reverse direction, with one of the electromagnetic clutches which is associated with the corresponding adjustable direction of one of the seat members connected to the motor, so that the corresponding seat member can be moved to an original seat position according to the stored counted positional data until the presently counted value of the corresponding reversible counter becomes equal to the stored counted value by the comparison of these values in the comparator when a return switch and the address switch allocated to the driver on the operation panel are operated.
However, in the conventional seat positioning device described above, since the rotating force of the reversible motor is transmitted via one of the electromagnetic clutches to the corresponding seat member actuator, a slip will occur between the electromagnetic clutch and output shaft of the motor whenever the motor starts or stops, engaged with each electromagnetic clutch. Once the slip occurs, there is a small deviation between the number of rotations of the reversible motor indicated by the corresponding reversible counter and actual displacement of the corresponding seat member along the adjustable direction. As repetitive start and stop of the reversible motor are carried out to adjust the entire seat position, an amount of deviations due to the recurrent slips is accumulated so that the respective reversible counters will not indicate actual set positions of the respective seat members. In this situation, if the reversible motor is driven by the control circuit via the motor drive circuit so as to make the contents of the individual reversible counters equal to the correspondingly stored values of the memory, the actually returned seat position does not coincide with the originally selected seat position by the original driver due to the accumulated deviations included in the contents of the corresponding reversible counter and consequential contents of the memory.